Tutorial - n8n Expressions

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        "content": "# Tutorial - Mastering n8n Expressions\n\nWelcome! You know what JSON is. Now, let's learn how to **use it**. This workflow teaches you how to pull data from one node and use it in another using n8n's powerful expressions.\n\n**What is an Expression?**\nAn expression is a small piece of code inside double curly braces `{{ }}` that gets replaced with a dynamic value when the workflow runs. It's the \"glue\" that connects your nodes.\n\n**How to use this tutorial:**\n1.  The first node, **\"Source Data\"**, contains all the data we will use. Execute it once to see what's inside.\n2.  Follow the path from top to bottom. Each node is a new lesson.\n3.  Read the sticky note for each lesson, then look at the node's configuration and its output to understand the concept."
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              "id": "12345",
              "name": "name",
              "type": "string",
              "value": "Alice"
            },
            {
              "id": "67890",
              "name": "age",
              "type": "number",
              "value": 30
            },
            {
              "id": "abcde",
              "name": "is_active",
              "type": "boolean",
              "value": true
            },
            {
              "id": "fghij",
              "name": "skills",
              "type": "array",
              "value": "[\"JavaScript\",\"Python\",\"n8n\"]"
            },
            {
              "id": "klmno",
              "name": "projects",
              "type": "array",
              "value": "[{\"name\":\"Project A\",\"status\":\"Done\"},{\"name\":\"Project B\",\"status\":\"In Progress\"}]"
            },
            {
              "id": "pqrst",
              "name": "contact",
              "type": "object",
              "value": "{\"email\":\"[email protected]\",\"phone\":null}"
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        "content": "## Our Data Source\n\nThis node holds all the sample data for our tutorial. Think of it as a filing cabinet. All the other nodes will be reaching into this cabinet to pull out specific pieces of information.\n\nTake a look at its output to familiarize yourself with the structure.\nWe have:\n- Simple text (`name`)\n- A number (`age`)\n- A list of skills (`skills`)\n- A list of complex projects (`projects`)\n- A nested contact object (`contact`)"
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      "name": "1. The Basics",
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        "content": "## Lesson 1: Accessing a Simple Value\n\nThis is the most common thing you'll do in n8n.\n\n**The Goal:** Get the user's name from the \"Source Data\" node.\n\n**The Expression:** `{{ $('Source Data').item.json.name }}`\n\n**Breakdown:**\n- `{{ ... }}`: Tells n8n \"this is a dynamic expression\".\n- `$('Source Data')`: Selects the node we want data from.\n- `.item.json`: Narrows it down to the JSON data of the current item.\n- `.name`: Selects the specific **key** we want the value of.\n\n**Other Possibility:**\n`{{ $json.name }}` would also work in this case, as `$json` accesses the data from the previous node."
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        "content": "## Lesson 3: Accessing an Array Element\n\nWhat if the data is in a list (an array)? You need to specify *which* item you want.\n\n**The Goal:** Get the user's *second* skill.\n\n**The Expression:** `{{ $('Source Data').last().json.skills[1] }}`\n\n**Breakdown:**\n- `...skills`: Selects the array of skills.\n- `[1]`: Selects the item at a specific position.\n- **IMPORTANT:** Arrays are \"zero-indexed\", which means the first item is `[0]`, the second is `[1]`, the third is `[2]`, and so on."
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        "content": "## Lesson 4: Accessing Nested Data\n\nSometimes, data is organized into objects within other objects.\n\n**The Goal:** Get the user's email address.\n\n**The Expression:** `{{ $('Source Data').last().json.contact.email }}`\n\n**Breakdown:**\n- `...contact`: First, we access the `contact` object.\n- `.email`: Then, we use another dot `.` to go one level deeper and get the value of the `email` key inside it."
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        "content": "## Lesson 5: Accessing Data in an Array of Objects\n\nThis is the ultimate test of the previous lessons!\n\n**The Goal:** Get the *status* of the *first* project in the list.\n\n**The Expression:** `{{ $('Source Data').last().json.projects[0].status }}`\n\n**Breakdown:**\n1.  `...projects`: We select the array of projects.\n2.  `[0]`: We pick the first object in that array.\n3.  `.status`: From that chosen object, we grab the value of the `status` key."
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              "name": "name_in_caps",
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              "value": "={{ $('Source Data').last().json.name.toUpperCase() }}"
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              "id": "67890",
              "name": "age_in_dog_years",
              "type": "number",
              "value": "={{ Math.round($('Source Data').last().json.age / 7) }}"
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        "content": "## Lesson 6: A Touch of Magic (JS Functions)\n\nYou can do more than just retrieve data; you can **manipulate and inspect it!**\n\n**The Expressions:**\n- **Transform Text:** `{{ $('Source Data').last().json.name.toUpperCase() }}`\n- **Do Math:** `{{ Math.round($('Source Data').last().json.age / 7) }}`\n- **Check Data Type:** `{{ typeof $('Source Data').last().json.age }}`\n\n**Breakdown:**\n- **`.toUpperCase()`**: A standard JavaScript function for strings.\n- **`Math.round(...)`**: The `Math` object gives you access to powerful math functions.\n- **`typeof`**: An operator that tells you what kind of data you're looking at (\"string\", \"number\", \"object\", etc.)."
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      "name": "9. The \"All Items\" View",
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        "content": "## Lesson 9: Working with Multiple Items (`$items` & Arrow Functions)\n\nWhat if a node outputs *multiple* items and you want to summarize them? `$items()` is your tool.\n\n**The Goal:** Get a single, comma-separated string of all the user's skills.\n\n**The Expression:** `{{ $('Split Out Skills').all().map(item `=>` item.json.skills).join(', ') }}`\n\n**What is `item => ...`?**\nThis is an **Arrow Function**, a shorthand for \"for each thing, do this\".\n- `item`: A temporary name for each item in the list as we loop over it.\n- =>: The \"arrow\" that separates the item from the action.\n- `item.json.skills`: The action to perform—in this case, get the skill value from the item."
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              "value": "=User {{ $('2. The n8n Selectors').last().json.user_name_from_first }} is {{ $('Source Data').last().json.age }}.\n\nTheir best skill is {{ $('3. Working with Arrays').last().json.second_skill }}.\n\nTheir first project was {{ $('Source Data').last().json.projects[0].name }}, which is now {{ $('5. The Combo Move').last().json.first_project_status }}.\n\nAll skills: {{ $('9. The \"All Items\" View').last().json.all_skills_string }}."
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        "content": "## 🎓 FINAL EXAM: Putting It All Together\n\nThis node uses everything we've learned to build a final summary object.\n\nLook at the expressions for each field. They pull data from different nodes and use different techniques you've just practiced.\n\n**Congratulations! You now have the foundational knowledge to link data and build powerful, dynamic workflows in n8n.**"
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        "content": "## Lesson 2: The n8n Selectors (`.first()`, `.last()`, `.all()`)\n\nIn the last lesson, we used `.item`. When there is only one output item from a node, this is equivalent to `.last()`. Using `.last()` explicitly is often safer and clearer.\n\n**The Goal:** Get the user's name using the `.last()` selector.\n\n**The Expression:** `{{ $('Source Data').last().json.name }}`\n\n**Why is this better?**\nIf a node ever returns multiple items, `.last()` guarantees you only get data from the very last one.\n\nIf you ever need to match the selected data with the input items, this is where `.item` cannot be replaced.\n\n**Other Selectors:**\n- **`.first()`**: Gets the data from the first item.\n- **`.all()`**: Gets data from ALL items, returning it as an array of objects. (This is different from `$items`!)"
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              "name": "contact_keys",
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              "value": "={{ Object.keys($('Source Data').last().json.contact) }}"
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        "content": "## Lesson 7: Inspecting Objects (`Object.keys()`)\n\nWhat if you have an object but you don't know what keys are inside it? `Object.keys()` comes to the rescue.\n\n**The Goal:** Get a list of all the keys inside the `contact` object.\n\n**The Expression:** `{{ Object.keys($('Source Data').last().json.contact) }}`\n\nThis is incredibly useful for dynamically processing data. It returns an **array** containing the names of the keys (e.g., `[\"email\", \"phone\"]`)."
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              "value": "={{ JSON.stringify($('Source Data').last().json.contact, null, 2) }}"
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        "content": "## Lesson 8: Utility Functions (`JSON.stringify()`)\n\nSometimes you need to convert a structured JSON object back into a clean, single string. This is common when sending data to another service, like in an AI prompt.\n\n**The Goal:** Turn the entire `contact` object into a formatted string.\n\n**The Expression:** `{{ JSON.stringify($('Source Data').last().json.contact, null, 2) }}`\n\n**Breakdown:**\n- **`JSON.stringify(...)`**: The function that does the conversion.\n- **`null, 2`**: These optional parameters tell it to \"pretty-print\" the string with an indentation of 2 spaces, making it readable."
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